pic: Whoops! Too much torque

[basicxman]

loading photo ...

[Nick Lawrence]

How did this happen? Too much cowbell?

-Nick

[JesseK]

I think by cowbell, we mean what was the motor setup + gear ratio into this wheel? Also, how did the wheel stall?

[Chris is me]

The outer rims of the wheel seem like a really odd way for this wheel to shear. Wouldn't the bolt holes loosen, the sprocket bend, etc. before the outer part of the wheel broke? How does that relieve the stress?

[Brandon Holley]

Pretty interesting failure. Definitely not typical from what I've seen out of the kit wheels in the past.

Still looks like it was due to the robot being pushed sideways in some manner.

-Brando

[Racer26]

Sure looks like a side-loading failure to me. A rotational-loading failure would more likely manifest itself in shattering spokes, or breaking the holes in the hub.

[Josh Fox]

Team RUSH had a couple wheels go like that during the past season, those bumps were pretty rough, but we did add reinforcements to them by cutting pieces of what I believe was 1/16" aluminum and placing them between each set of spokes.

I don't fully understand what you mean by side-loading, so I'm not sure if that's the same as this, but I think the general belief is that our failures were due to the forces of impact on the wheels when they hit the ground.

[Ether]

Originally Posted by Josh Fox

I don't fully understand what you mean by side-loading

A force parallel to the wheel's axis I presume.

[Josh Fox]

That's what I assumed, I was just thinking that an impact force would be more likely to have this effect on the wheel, since it reflects what we saw happen in our own wheels this year.

[Ether]

Originally Posted by Josh Fox

That's what I assumed, I was just thinking that an impact force would be more likely to have this effect on the wheel

"load" can include impact loads.

You get hit hard in the side, the impact creates a momentary side load (especially if the bottom of the wheel is against the bump or the goal ramp)

[TroyCDH]

Neat picture. As others say, my guess is not torque but a thump coming down of a ramp etc.

I will add for fun--possible plastic "creep". If that robot has been strapped in real tight to a shipping crate for what? 7 months now...that could cause some high stress points that now show up after standard use.

Troy

[Chris is me]

The odd thing about this is that 2200 had an omnidrectional robot that could not cross the bump. Perhaps their preseason prototype has enough power to break wheels by pushing?

[BEEKMAN]

Originally Posted by Ether

A force parallel to the wheel's axis I presume.

Correct:

Axle-Wheel-Load
_
| |
| |
---| | /___\
---| | \ /
| |
|_|

Woot ASCII Art


EDIT: It messes up my spacing.......

[Chris is me]

Correct:

Axle        Wheel     Load
                  _
                 | |
                 | |
-----------------| |    /_________\
-----------------| |    \        /
                 | |
                 |_|

Fixed art above.

[sithmonkey13]

1178 had something kind of like this happen at an off-season event (any Venturing Scouts might know about the Fall Fun Rally held in St. Louis, Boeing always asks us to come out to their events and show off a competition bot). After several hours of driving on asphalt, a scout drove the robot off the road, where one wheel got stuck. The scout proceeded to show the joystick all the way forward, and bent the sprocket and sheared off all the bolst holding the sprocket to the wheel. Needless to say, we were done driving that day.